The construct of attention plays a central role in theories of memory encoding. However, until recently little research in this area has focused on implicit memory. This proposal investigates the role of attention in perceptual implicit memory. What prior research exists presents conflicting results, with some studies reporting large effects of attentional manipulations on perceptual priming and others reporting no effects. This proposal identifies systematic differences between the attentional manipulations in these two sets of studies, giving rise to three hypotheses. One hypothesis is that manipulations of attention affect perceptual priming only to the extent that they disrupt stimulus identification. A second hypothesis attributes reduced priming to the disruptive effects of distractor selection. A third hypothesis states that perceptual priming relies on modality-specific but not central aspects of attention, thus predicting that perceptual priming is affected by intra-modal but not cross-modal manipulations of attention. Four experiments are proposed to determine which hypothesis best accounts for the divergent results. In the study phase, subjects will encode words under either full or divided attention conditions. Attention will be divided intra-modally or cross- modally, and study words and distracting stimuli will be present synchronously or asynchronously. Perceptual implicit memory will be assessed with perceptual identification and word-fragment completion.